• A deep-junction SPAD with a p-implant/HVNW junction enhances NIR sensitivity, achieving a PDP of 6.8% at 905 nm.
• Optimizing guard ring design improves fill factor from 20.7% to 39.1% when active diameter increases from 5 to 10 μm, boosting peak PDE from 13.3% to 25.8%.
• A field polysilicon gate structure connected to the p+ anode reduces dark count rate by 76.6%.
• At 5 V excess bias, the device achieves a low DCR of 2.12 cps/μm2, an afterpulsing probability of 1.2%, and a timing jitter of 216 ps.